Primates as our closest relatives form an indispensable resource for biomedical research with direct and immediate relevance to humans. Small (< 500 g) New World primate species offer an array of research advantages relative to more traditionally-used Old World monkeys (OWMs), including significantly lower costs in terms of space and maintenance requirements, several times higher colony productivity, and an accelerated life history including earlier sexual maturity and senescence. With this in mind, we propose to develop the common marmoset as a major primate research model by developing techniques for establishing and maintaining them in barrier colonies and by developing tools to monitor and manage a health problem (chronic lymphocytic enteritis, CLE) to which some colonies have been prone. Barrier colonies have proven indispensible in enhancing in laboratory rodent research by improving phenotypic uniformity and enhancing the repeatability of experimental results within and among laboratories. The ability to closely monitor animal health is also invaluable to success in research colony management. This project is particularly timely, as high coverage whole genome sequencing of the marmoset has recently been completed. Thus new molecular tools for marmoset research can now be easily developed. We will accomplish our goals by performing the following specific aims: (1): Establish and evaluate procedures for developing barrier colonies of clean, healthy animals by two methods (a) utilizing existing, healthy breeding pairs, screened and treated for specific pathogens maintained within a microbiological barrier; and (b) develop procedures for establishing clean colonies from caesarean-derived, hand-reared barrier-maintained animals. An important outcome of this research will be an evaluation of which offers the better approach; (2) develop noninvasive markers of gastrointestinal inflammation, to facilitate monitoring and management of colony health; and (3) perform and evaluate a comprehensive molecular analysis of the affected intestinal mucosal microbiota of animals with CLE compared with unaffected controls along vAXh all barrier-maintained versus conventionally-reared animals. This latter aim will potentially yield insight into the etiology and diagnosis of CLE and also serve as a surveillance tool for monitoring colony health.